Rock is enjoying a resurgence at the top of the album charts, thanks to some much-anticipated veteran acts.

System of a Down (search) debuted at No. 1 on latest Billboard album chart, according to sales figures released Wednesday. The band sold approximately 453,000 copies of "Mezmerize," their first album in three years.

This is the fifth week in a row a rock act debuted at the top of the charts: The Dave Matthews Band (search), Nine Inch Nails (search) and Bruce Springsteen (search) this month, and Rob Thomas (search) from Matchbox Twenty in the last week in April. Other rockers such as Weezer (search) and Beck (search) have also debuted strongly, if not at the No. 1 spot, in recent weeks.

Along with the continued success of 2004 strong sellers like Green Day (search) and U2 (search), rock has had a stronger presence atop the charts this year, reversing a trend that saw hip-hop, R&B or pop acts dominate most of the top positions. It's also comes at a time when the rock has been losing its audience at radio, as more stations drop the format in favor of urban music.

"It is unusual since the past few weeks before that, you've had people like Mariah Carey, 50 Cent, Kelly Clarkson (at the top)," said Doug Broad, executive editor at Spin magazine.

"A lot of rock bands up there at once is pretty impressive, and it might kind of speak to a trend to people getting back to that music. ... I think it started kind of with Green Day and U2 exploding and doing well."

But Geoff Mayfield, director of charts at the music trade magazine Billboard, says the success shows that rock music isn't as endangered as some have made it out to be.

"It's just a reminder that anytime you read the 'rock is dead' obituary, that was premature story," he said. "Each of those music genres gets to take turns — sometimes you're hot, sometimes you're not."

It may also be a case of absence making the heart grow fonder. The artists and bands that have debuted at the top of the charts of late have also not put out albums for at least two or three years, which may help account for the strong sales.

"It's a time when there are a lot of big event rock albums coming out," said Broad.

Still, veteran producer Rick Rubin, who produced System of a Down's "Mezmerize" and this week's debut from Audioslave, "Out of Exile," says there's no new trend — just better music.

"There are not a lot of great rock acts at the moment, and the ones that we've talked about, Weezer has been around for 10 years, Nine Inch Nails have been around for 10 years," he said. "These are the blue-chip brands of rock music, all putting out records now, and you can include U2 in that group."

Rubin said low sellers over the past year, especially among younger acts, "really has more to do with the quality of the music than anything else."

"These are the real quality acts," he said of the recent chart-toppers. "These are real artists who are trying to make great albums."

The other acts rounding out the top five this week were from country's Toby Keith's "Honkytonk University," which debuted at No. 2 with 283,000 albums sold; Mariah Carey's "The Emancipation of Mimi," which remained in third place with 173,000 copies sold; the Dave Matthews Band, which fell from No. 1 to No. 4 with 158,000 copies sold; and R&B singer Kem, whose second album — appropriately titled "Album II" — sold 140,000 to debut at No. 5.